Method and apparatus for activating carriers in mobile communication system

ABSTRACT

A method for activating a carrier by a User Equipment (UE) in a mobile communication system supporting carrier aggregation is provided. The UE receives a Down-Link (DL) assignment from an Evolved Node B (ENB), and determines whether to activate a carrier based on the DL assignment. By doing so, the UE may perform carrier activation rapidly and efficiently.

PRIORITY

This application is a National Stage application under 35 U.S.C. §371 ofan International application filed on Jan. 19, 2011 and assignedapplication No. PCT/KR2011/000397, and claims the benefit under 35U.S.C. §365(b) of a Korean patent application filed in the KoreanIndustrial Property Office on Jan. 19, 2010 and assigned Serial No.10-2010-0004957, a Korean patent application filed in the KoreanIndustrial Property Office on Mar. 17, 2010 and assigned Serial No.10-2010-0023781, a Korean patent application filed in the KoreanIndustrial Property Office on Apr. 12, 2010 and assigned Serial No.10-2010-0033270, and a Korean patent application filed in the KoreanIndustrial Property Office on May 10, 2010, and assigned Serial No.10-2010-0043689, the entire disclosures of each of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication system. Moreparticularly, the present invention relates to a method and apparatusfor activating carriers by a terminal or a User Equipment (UE) for whicha plurality of Down-Link (DL) carriers and Up-Link (UL) carriers areconfigured.

2. Description of the Related Art

Generally, mobile communication systems have been developed to providecommunication services while enabling mobility of users. Due to therapid development of technologies, the mobile communication systems nowcan provide not only voice communication services but also high-speeddata communication services.

Standardization for Long Term Evolution (LTE) as one of thenext-generation mobile communication systems is now underway in the 3rdGeneration Partnership Project (3GPP). LTE, expected to becommercialized in about 2010, is technology for implementing high-speedpacket-based communication having a data rate of as high as 100 Megabitsper second (Mbps), which is higher than the currently available datarate, and its standardization has almost been completed. With the LTEstandardization being in its final stage, an LTE-Advanced (LTE-A)communication system is under discussion, which further improves thedata rate by combining several new technologies with the LTEcommunication system. A typical one of the technologies to be newlyintroduced may include Carrier Aggregation (CA). CA is a technology inwhich a User Equipment (UE) transmits/receives data using a plurality ofcarriers. More specifically, a UE performs high-speed communication bytransmitting/receiving data through a specific cell having aggregatedcarriers, usually a cell belonging to the same Node B as that of the UE.CA includes a carrier configuration procedure of delivering informationabout carriers to be aggregated to a UE, and a carrier activationprocedure of activating configured carriers at an appropriate time. Thereason for using the duplex procedure—carrier configuration and carrieractivation—is to minimize the battery consumption of a UE by activatingonly some of configured carriers and turning off transceivers associatedwith deactivated carriers when data transmission/reception is inactive.Preferably, therefore, the carrier activation procedure should beperformed as quickly as possible.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide an apparatus and method for synchronizing useinformation between mobile communication terminals comprisingshort-range wireless communication units.

Exemplary embodiments of the present invention provide a method andapparatus for rapidly activating carriers in a mobile communicationsystem.

Exemplary embodiments of the present invention provide a carrieractivation method and apparatus for minimizing inefficiency caused bytransmitting carrier activation commands with a Down-Link (DL)assignment in a mobile communication system.

In accordance with an aspect of the present invention, a method foractivating a carrier by a User Equipment (UE) in a mobile communicationsystem supporting carrier aggregation is provided. The method includesreceiving a DL assignment from an Evolved Node B (ENB), and determiningwhether to activate a carrier based on the DL assignment.

In accordance with another aspect of the present invention, a UE in amobile communication system supporting carrier aggregation is provided.The UE includes a receiver for receiving a DL assignment from an ENB,and a controller for determining whether to activate a carrier based onthe DL assignment.

In accordance with another aspect of the present invention, a method foractivating a carrier by a UE in a mobile communication system supportingcarrier aggregation is provided. The method includes receiving areceiving a DL assignment from an ENB over a specific carrier, andtemporarily activating at least one carrier having not been activated,based on the DL assignment.

In accordance with another aspect of the present invention, a UE in amobile communication system supporting carrier aggregation is provided.The UE includes a receiver for receiving a DL assignment from an ENB,and a controller for temporarily activating at least one carrier havingnot been activated, if the DL assignment is received over a specificcarrier.

In accordance with another aspect of the present invention, a method foractivating a carrier by a UE in a mobile communication system supportingcarrier aggregation is provided. The method includes receiving a DLassignment from an ENB over a specific carrier, determining whether theDL assignment indicates a carrier activation command, and activating atleast one carrier corresponding to the carrier activation command, ifthe DL assignment indicates the carrier activation command.

In accordance with another aspect of the present invention, a UE in amobile communication system supporting carrier aggregation is provided.The UE includes a receiver for receiving a DL assignment from an ENB,and a controller for determining whether the DL assignment indicates acarrier activation command, and activating at least one carriercorresponding to the carrier activation command if the DL assignmentindicates the carrier activation command.

In accordance with another aspect of the present invention, a method formeasuring a carrier by a UE in a mobile communication system supportingcarrier aggregation is provided. The method includes receiving aparameter for measurement of a carrier in a deactivated state, from anENB, in performing measurement on a carrier in an activated state,determining a measurement interval and a measurement period taking aDiscontinuous Reception (DRX) operation into account and measuring thecarrier at the determined measurement interval for the determinedmeasurement period, and in performing measurement on the carrier in thedeactivated state, determining a measurement interval and a measurementperiod using a parameter related to at least one of a measurementinterval and a measurement period indicated by the ENB, and measuringthe carrier at the determined measurement interval for the determinedmeasurement period.

In accordance with another aspect of the present invention, a UserEquipment (UE) in a mobile communication system supporting carrieraggregation is provided. The UE includes a receiver for receiving aparameter for measurement of a carrier in a deactivated state, from anENB, and a controller for, in performing measurement on a carrier in anactivated state, determining a measurement interval and a measurementperiod taking a DRX operation into account and measuring the carrier atthe determined measurement interval for the determined measurementperiod, and in performing measurement on the carrier in the deactivatedstate, determining a measurement interval and a measurement period usinga parameter related to at least one of a measurement interval and ameasurement period indicated by the ENB, and measuring the carrier atthe determined measurement interval for the determined measurementperiod.

In accordance with another aspect of the present invention, a method foractivating a carrier by a UE in a mobile communication system supportingcarrier aggregation is provided. The method includes receiving a carrieractivation command from an ENB, determining a time at which an operationrequired for carrier activation is to be performed, and performing theoperation required for carrier activation at the determined time.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating a configuration of a Long TermEvolution (LTE) mobile communication system according to an exemplaryembodiment of the present invention;

FIG. 2 is a diagram illustrating protocol architecture of an LTE mobilecommunication system according to an exemplary embodiment of the presentinvention;

FIG. 3 is a diagram illustrating Carrier Aggregation (CA) in an LTEmobile communication system according to an exemplary embodiment of thepresent invention;

FIG. 4 is a flow diagram illustrating a carrier configuration andcarrier activation process in an LTE mobile communication systemaccording to an exemplary embodiment of the present invention;

FIG. 5 is a diagram illustrating a structure of a Down-Link (DL)assignment in an LTE mobile communication system according to anexemplary embodiment of the present invention;

FIG. 6 is a diagram illustrating an operation of activating DL carriersusing a carrier indicator according to an exemplary embodiment of thepresent invention;

FIG. 7 is a flowchart illustrating an operation of a User Equipment (UE)according to a first exemplary embodiment of the present invention;

FIG. 8 is a diagram illustrating a structure of a Downlink ControlInformation (DCI) Format 1C according to an exemplary embodiment of thepresent invention;

FIG. 9 is a diagram illustrating a structure of a carrier activationcommand based on a DCI Format 1C according to an exemplary embodiment ofthe present invention;

FIG. 10 is a flowchart illustrating an operation of a UE according to asecond exemplary embodiment of the present invention;

FIG. 11 is a diagram illustrating an example of an operation accordingto a third exemplary embodiment of the present invention;

FIG. 12 is a flowchart illustrating an operation of a UE according tothe third exemplary embodiment of the present invention;

FIG. 13 is a diagram illustrating an example of an operation accordingto a fourth exemplary embodiment of the present invention;

FIG. 14 is a flowchart illustrating an operation of a UE according tothe fourth exemplary embodiment of the present invention;

FIG. 15 is a flowchart illustrating an operation of a UE according to afifth exemplary embodiment of the present invention;

FIG. 16 is a diagram illustrating a UE to which the present invention isapplied according to an exemplary embodiment of the present invention;

FIG. 17 is a diagram illustrating an example of a measurement processaccording to an exemplary embodiment of the present invention;

FIG. 18 is a diagram illustrating an example of an operation accordingto a sixth exemplary embodiment of the present invention;

FIG. 19 is a flowchart illustrating an operation of a UE according tothe sixth exemplary embodiment of the present invention;

FIG. 20 is a diagram illustrating a mismatch between aggregated DLcarriers in frame timing according to an exemplary embodiment of thepresent invention;

FIG. 21 is a diagram illustrating an example of an operation accordingto a seventh exemplary embodiment of the present invention;

FIG. 22 is a flow diagram illustrating the overall operation accordingto the seventh exemplary embodiment of the present invention;

FIG. 23 is a flowchart illustrating an operation of a UE according tothe seventh exemplary embodiment of the present invention;

FIG. 24 is a flowchart illustrating an operation of a UE according to aneighth exemplary embodiment of the present invention;

FIG. 25 is a flowchart illustrating another operation of a UE accordingto the eighth exemplary embodiment of the present invention;

FIG. 26 is a diagram illustrating a UE according to an exemplaryembodiment of the present invention;

FIG. 27 is a diagram illustrating a process of scrambling anddescrambling a DL traffic channel according to an exemplary embodimentof the present invention;

FIG. 28 is a flowchart illustrating an operation of an Evolved Node B(ENB) according to a ninth exemplary embodiment of the presentinvention;

FIG. 29 is a flowchart illustrating an operation of a UE according tothe ninth exemplary embodiment of the present invention;

FIG. 30 is a diagram illustrating an ENB for the ninth exemplaryembodiment of the present invention;

FIG. 31 is a diagram illustrating a UE for the ninth exemplaryembodiment of the present invention;

FIG. 32 is a diagram illustrating an example of an operation ofdeactivating activated carriers according to a tenth exemplaryembodiment of the present invention;

FIG. 33 is a flowchart illustrating an operation of a UE according tothe tenth exemplary embodiment of the present invention;

FIG. 34 is a flowchart illustrating another operation of a UE accordingto the tenth exemplary embodiment of the present invention;

FIG. 35 is a diagram illustrating an example of Radio Frequency (RF)reconfiguration according to an exemplary embodiment of the presentinvention;

FIG. 36 is a flow diagram illustrating an example of an operation ofreconfiguring RF according to an eleventh exemplary embodiment of thepresent invention;

FIG. 37 is a diagram illustrating an example of an RF reconfigurationwindow according to an exemplary embodiment of the present invention;

FIG. 38 is a flowchart illustrating an operation of a UE according tothe eleventh exemplary embodiment of the present invention;

FIG. 39 is a flowchart illustrating another operation of a UE accordingto the eleventh exemplary embodiment of the present invention;

FIG. 40 is a flowchart illustrating an operation of an ENB according tothe eleventh exemplary embodiment of the present invention;

FIG. 41 is a flowchart illustrating a UE operation of selecting asubframe in which RF is to be reconfigured during carrier activation anddeactivation according to an exemplary embodiment of the presentinvention;

FIG. 42 is a diagram illustrating a UE according to the eleventhexemplary embodiment of the present invention; and

FIG. 43 is a diagram illustrating an ENB according to the eleventhexemplary embodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Exemplary embodiments of the present invention will now be described indetail with reference to the accompanying drawings. The presentinvention may, however, be embodied in many different forms and shouldnot be construed as being limited to the exemplary embodiments set forthherein.

In the following detailed description of exemplary embodiments of thepresent invention, 3^(rd) Generation Partnership Project (3GPP) EvolvedUniversal Mobile Telecommunication System (UMTS) Terrestrial RadioAccess (EUTRA) (or Long Term Evolution (LTE)), or Advanced E-UTRA (orLTE-A) will be mainly taken into account. However, it will be understoodby those of ordinary skill in the art that the gist of the presentinvention may be applied to any other communication systems havingsimilar technical backgrounds and channel formats with a slightmodification without departing from the spirit and scope of theinvention.

Exemplary embodiments of the present invention relates to a method andapparatus for efficiently activating carriers.

Prior to a detailed description of exemplary embodiments of the presentinvention, an LTE mobile communication system will be described in moredetail with reference to FIGS. 1, 2 and 3. FIG. 1 illustrates aconfiguration of an LTE mobile communication system.

Referring to FIG. 1, a wireless access network of an LTE mobilecommunication system includes Evolved Node Bs (ENBs) 105, 110, 115, and120, a Mobility Management Entity (MME) 125, and a Serving-Gateway(S-GW) 130. A User Equipment (UE) 135 accesses external networks via theENBs 105˜120, and the S-GW 130.

The ENBs 105˜120 correspond to the legacy Node Bs of a UMTS system. TheENBs 105˜120 are connected to the UE 135 by wireless channels. Since alluser traffics including real-time services such as Voice over InternetProtocol (IP) (VoIP) are serviced through shared channels, a device forperforming scheduling by collecting state information of UEs isrequired, and this scheduling operation is covered by the ENBs 105˜120.Commonly, one ENB controls a plurality of cells. To implement a datarate of a maximum of 100 Megabits per second (Mbps) per cell, LTE usesOrthogonal Frequency Division Multiplexing (OFDM) as wireless accesstechnology in a bandwidth of a maximum of 20 MegaHertz (MHz). Inaddition, LTE employs Adaptive Modulation & Coding (AMC) that adaptivelydetermines a modulation scheme and a channel coding rate depending onthe channel condition of the UE 135. The S-GW 130, a device forproviding data bearers, generates and removes data bearers under controlof the MME 125. The MME 125, a device responsible for various controlfunctions, is connected to a plurality of ENBs.

FIG. 2 illustrates protocol architecture of an LTE mobile communicationsystem according to an exemplary embodiment of the present invention. Aradio protocol will be described in brief with reference to FIG. 2.

Referring to FIG. 2, a radio protocol of the LTE system includes PacketData Convergence Protocols (PDCPs) 205 and 240, Radio Link Controls(RLCs) 210 and 235, and Medium Access Controls (MACs) 215 and 230. ThePDCPs 205 and 240 take charge of IP header compression/decompression,and the RLCs 210 and 235 reconstruct PDCP Protocol Data Units (PDUs) inan appropriate size, and perform an Automatic Repeat reQuest (ARQ)operation. The MACs 215 and 230 are connected to several RLC-layerdevices constructed in one UE, and perform an operation of multiplexingRLC PDUs to a MAC PDU and demultiplexing RLC PDUs from a MAC PDU.Physical (PHY) layers 220 and 225 perform an operation ofchannel-coding, modulating, and scrambling upper layer data into an OFDMsymbol and transmitting the OFDM symbol on a wireless channel, or anoperation of descrambling, demodulating, and channel-decoding an OFDMsymbol received over a wireless channel and delivering the decoded OFDMsymbol to their respective upper layers. The transmitted data beinginput to a protocol entity is referred to as a Service Data Unit (SDU),while the transmitted data being output from the protocol entity isreferred to as a Protocol Data Unit (PDU).

FIG. 3 illustrates Carrier Aggregation (CA) in an LTE mobilecommunication system according to an exemplary embodiment of the presentinvention. CA will be described in brief with reference to FIG. 3.

Generally, in one ENB, a plurality of carriers are transmitted andreceived over several frequency bands. For example, when a carrier 315with a center frequency=f1 and a carrier 310 with a center frequency=f2are transmitted in an ENB 305, one UE 330 transmits/receives data usingone of the two carriers. However, a UE 330 having a CA capability(hereinafter referred to as a ‘CA UE’) may transmit/receive data usingseveral carriers at the same time. An ENB may increase a data rate of aCA UE by allocating more carriers to the CA UE depending on thecircumstances. Supposing that one Down-Link (DL) carrier and one Up-Link(UL) carrier transmitted/received in one ENB constitute one cell in thetraditional sense, the term ‘CA’ may be considered that a UEtransmits/receives data through several cells at the same time. Themaximum data rate by CA increases with the number of aggregatedcarriers. In the following description, a UE's receiving of data throughan arbitrary DL carrier or transmitting of data through an arbitrary ULcarrier may be equivalent to transmitting/receiving data using a controlchannel and a data channel provided by a cell corresponding to a centerfrequency and a frequency band characterizing the carrier.

FIG. 4 illustrates a carrier configuration and carrier activationprocess in an LTE mobile communication system according to an exemplaryembodiment of the present invention.

Referring now to FIG. 4, CA is dualized into a process of deliveringinformation about carriers to a UE, and a process of activatingcarriers. For example, in step 415, an ENB 410 provides informationabout carriers to be aggregated to an arbitrary CA UE 405. Theinformation includes a center frequency, a bandwidth (BW), a PhysicalCell ID (PCI), etc. of a carrier. A UE memorizes the receivedinformation, and if needed, performs an operation of acquiring DLsynchronization of a cell associated with the carrier. Acquiring DLsynchronization of an arbitrary cell means acquiring framesynchronization by receiving a synchronization channel of the cell. Ifthe amount of data to be transmitted to the UE 405 increases, the ENB410 activates a carrier configured for the UE 405 in step 420, andtransmits data to the UE 405 even over the activated carrier in step425, thereby increasing the data rate. In the following description,aggregating carriers may be equivalent to aggregating cells specified tothe carriers. Delivering information about carriers and cells to beaggregated to a UE is expressed as configuring the carriers. Inaddition, a carrier aggregated for a UE is called a Component Carrier(CC). For convenience of description, the terms ‘carrier’, ‘cell’ and‘CC’ are used herein with the same meaning.

A maximum of five CCs may be aggregated for one UE. For efficientcommunication, it is preferable to configure as many carriers aspossible for one UE, so as to rapidly activate the carriers for datatransmission/reception in case of an increase in the amount of traffic,and deactivate the carriers in case of a decrease in the amount oftraffic. In exemplary embodiments of the present invention, carrieractivation is performed as quickly as possible by making a carrieractivation command using a physical layer signal. To be more specific, acarrier activation command is transmitted over a DL Physical DownlinkControl Channel (PDCCH). In addition, a carrier activation command isdelivered using a DL assignment containing DL scheduling information.

FIG. 5 illustrates a structure of a DL assignment in an LTE mobilecommunication system according to an exemplary embodiment of the presentinvention.

A DL assignment includes scheduling information 505, Hybrid ARQ (HARQ)information 510, a Carrier Indicator (CI) 515, and a Cyclic RedundancyCheck (CRC) code 520. The scheduling information 505 includesinformation about resources allocated to a DL Physical Downlink SharedChannel (PDSCH) over which DL data is to be transmitted, and informationabout a Modulation Coding Scheme (MCS) to be applied for DL datatransmission.

The HARQ information 510 includes an identifier of an HARQ processor tobe used for DL data transmission. The above information is informationthat a UE should know to receive DL data over a PDSCH, and forconvenience of description, the above information will be referred to asPDSCH-related information. The CRC 520 is used to determineexistence/nonexistence of an error in DL assignment information, andincludes a result value of a CRC operation on information including anidentifier of a UE, called a Cell-Radio Network Temporary Identity(C-RNTI). Thus, even though an arbitrary UE receives a DL assignment ofanother UE, a CRC fail occurs, and a CRC OK occurs only for the DLassignment transmitted to the UE itself So, the CRC code value may alsoallow a UE to receive only the DL assignment transmitted to the UEitself.

The carrier indicator 515 is 3-bit information indicating over whichcarrier the DL data is to be transmitted. When carriers are aggregatedfor the UE 405, the ENB 410 allocates a 3-bit identifier to eachcarrier, and the carrier indicator 515 indicates which carrier the DLassignment schedules. A first exemplary embodiment of the presentinvention provides a method of instructing activation of a DL carrierusing the carrier indicator.

First Exemplary Embodiment

In the first exemplary embodiment of the present invention, an ENBinstructs a UE to activate a specific carrier, using a carrier indicatorfield of a DL assignment. In the first exemplary embodiment of thepresent invention, the DL assignment may be either a common DLassignment or a carrier activation command. If a carrier indicated inthe carrier indicator 515 of the DL assignment is a carrier havingalready been activated, the DL assignment is a common DL assignment.That is, the UE 405 receives DL data from the carrier indicated in thecarrier indicator 515 of the DL assignment according to the schedulinginformation 505 and the HARQ information 510 of the DL assignment. If acarrier indicated in the carrier indicator 515 of the DL assignment is acarrier having not been activated yet, the DL assignment is a carrieractivation command. The UE 405 activates the carrier indicated in thecarrier indicator 515 of the carrier activation command.

FIG. 6 illustrates an operation of activating DL carriers using acarrier indicator according to an exemplary embodiment of the presentinvention.

Activating an arbitrary carrier means turning on a receiver for thecarrier and starting receiving a signal from the carrier. In otherwords, a UE 405 receives PDCCH and PDSCH only from the activatedcarriers among the configured carriers, and receives no PDCCH and PDSCHfrom the deactivated carriers. For example, two DL carriers—a DL CCx 605and a DL CCy 610—are configured for one UE 405, and the DL CCx 605 isactivated. In FIG. 6, a square represents a subframe, a gray squarerepresents an activated carrier in a subframe, and a white squarerepresents a deactivated carrier in a subframe. The UE 405 continuouslyreceives a PDCCH of an activated carrier, e.g., the DL CCx. Uponreceiving a DL assignment with a carrier indicator 515, in which acarrier having already been activated, e.g., DL CCx, is included, overthe DL CCx at an arbitrary time 615, the UE 405 receives a PDSCH overthe DL CCx according to scheduling information 505 and HARQ information510 in the DL assignment, determining that the received DL assignment isa common DL assignment. Thereafter, if a new DL assignment is receivedover the DL CCx at an arbitrary time 620 and a carrier indicator 515 ofthe received DL assignment indicates a carrier having not been activatedyet, e.g., DL CCy, then the UE 405 activates the DL CCy indicated by thecarrier indicator 515, determining that the received DL assignment is acarrier activation command.

As described above, the UE 405 does not receive a signal of adeactivated DL carrier. However, if a deactivated DL carrier isactivated using a carrier indicator of a DL assignment as proposed inthe present invention, the UE 405 does not receive a signal of a DLcarrier to be activated until it completes analysis of the carrieractivation command, causing a waste of PDSCH-related informationincluded in the carrier activation command. To be more specific, inorder to fully receive a PDSCH of an arbitrary carrier, the UE 405should receive the carrier beginning from a start point of a subframe.Despite normal reception of a carrier activation command, since thereception of the carrier activation command is completed after a lapseof a significant part of a subframe, the UE 405 cannot receive a PDSCHfrom a newly activated carrier in the subframe. To address these andother problems, in the present exemplary embodiment, if an arbitrary DLassignment is a carrier activation command, PDSCH-related informationincluded therein is defined as a specific carrier among the carriershaving already been activated, rather than a carrier indicated by thecarrier indicator 515. In other words, if a carrier indicator 515 of aDL assignment indicates a carrier having already been activated,PDSCH-related information in the DL assignment is used to receive aPDSCH over the indicated carrier, and if a carrier indicator 515 of a DLassignment indicates a deactivated carrier, the UE 405 activates thedeactivated carrier and receives a PDSCH over a specific carrier otherthan the carrier indicated by the carrier indicator 515.

FIG. 7 illustrates an operation of a UE according to the first exemplaryembodiment of the present invention.

Upon receiving a DL assignment in step 705, a UE 405 checks a carrierindicator 515 of the received DL assignment in step 710. If a carrierindicated in the carrier indicator 515 is a carrier having already beenactivated, the UE 405 proceeds to step 715, and if the indicated carrieris a carrier having not been activated yet, the UE 405 proceeds to step720. In step 715, the UE 405 receives a PDSCH of the carrier indicatedin the carrier indicator 515 using the PDSCH-related information of theDL assignment. In step 720, the UE 405 activates the carrier indicatedin the carrier indicator 515. In step 725, the UE 405 receives a PDSCHfrom a specific carrier using the PDSCH-related information of thereceived DL assignment. The specific carrier may be a carrierpredetermined by an implicit rule. For example, a carrier alwaysmaintaining its activated state, i.e., an anchor carrier to which the UE405 is anchoring, can be used for the above purpose. That is, uponreceiving a DL assignment indicating a carrier having not been activatedyet, the UE 405 receives a PDSCH of an anchor carrier using thePDSCH-related information of the DL assignment. Also, the ENB 410 mayexplicitly inform the UE 405 of which carrier it will use for the abovepurpose, in a call setup process or a CA process. Otherwise, the carriermay be a carrier over which the DL assignment is received. Uponreceiving a DL assignment indicating a carrier having not been activatedyet, the UE 405 receives a PDSCH of the pre-designated carrier, or acarrier over which the DL assignment was received, using PDSCH-relatedinformation of the DL assignment.

Second Exemplary Embodiment

A second exemplary embodiment of the present invention provides a methodof transmitting a carrier activation command using a Downlink ControlInformation (DCI) format 1C.

FIG. 8 illustrates a structure of a DCI format 1C according to anexemplary embodiment of the present invention.

A DCI format 1C is a small-sized DL assignment format defined to be usedin the case where HARQ information such as paging message and systeminformation is not applied and only limited resources are allocated. Asize of the DCI format 1C is variable according to the system bandwidth,and in the minimum system bandwidth, the DCI format 1C excluding a CRCcode has eight bits. The DCI format 1C includes transmission resourceallocation information 805, MCS information 810, and CRC 815. The CRCfield 815 includes a CRC operation result masked with an RNTI associatedwith a plurality of unspecified UEs, such as a Paging (P)-RNTI or aSystem Information (SI)-RNTI. The P-RNTI or SI-RNTI is an RNTI definedfor a paging message or system information, and is defined per cell.

FIG. 9 illustrates a structure of a carrier activation command based ona DCI format 1C according to an exemplary embodiment of the presentinvention.

In the second exemplary embodiment of the present invention, a carrieractivation command is transmitted/received using a DCI format 1C. Todistinguish the carrier activation command from the common DL assignmenttransmitted over the DCI format 1C, a CRC field 915 of the carrieractivation command includes a CRC operation result masked with a C-RNTIor a UE's unique identifier. The carrier activation command includes a5-bit bitmap 905, and the bits of the bitmap 905 are mapped to carriersconfigured for the UE 405 on a one-to-one basis. The mappingrelationship is set by a specific rule or an explicit indication in theCA process. If a bit of the bitmap 905 is set to ‘1’, it means that acarrier mapped to the bit is activated, and if a bit of the bitmap 905is set to ‘0’, it means that a carrier mapped to the bit is deactivated.Bits 910 are reserved for future use and will not be further describedherein.

FIG. 10 illustrates an operation of a UE according to the secondexemplary embodiment of the present invention.

In step 1005, a UE 405 receives a CA message from an ENB 410. Based oninformation in the received CA message, the UE 405 configures carriersto be aggregated, and determines to which bits of a bitmap the carrierswill be mapped. After configuring carriers depending on the CA message,the UE 405 starts receiving a DCI format 1C over a PDCCH in step 1010.In step 1015, the UE 405 performs a CRC operation by masking the DCIformat 1C received from the ENB 410 with its C-RNTI. In step 1020, theUE 405 checks occurrence/non-occurrence of an error referring to the CRCoperation result. In the absence of an error, since the received DCIformat 1C means a carrier activation command, the UE 405 proceeds tostep 1025. However, in case of a CRC error, the UE 405 repeats a processof receiving a DCI format 1C in the next subframe, performing a CRCoperation, and determining reception/non-reception of a carrieractivation command. In step 1025, the UE 405 analyzes bitmap informationof the received carrier activation command and activates a carrier, abit mapped to which is set to ‘1’ In step 1030, the UE 405 deactivates acarrier, a bit mapped to which is set to ‘0’.

Third Exemplary Embodiment

FIG. 11 illustrates an example of an operation according to a thirdexemplary embodiment of the present invention.

CA undergoes a procedure consisting of two steps, carrier configurationand carrier activation, in order to minimize power consumption. Sincecarriers having similar bands are generally driven by one transceiver,there is no significant difference in power consumption, even thoughonly some carriers are activated and the other carriers are deactivated.The third exemplary embodiment of the present invention provides amethod of grouping carriers having similar frequency bands, andactivating/deactivating the carriers on a group-by-group basis.

When transmitting a control message for carrier configuration to the UE405, the ENB 410 indicates carriers belonging to the same group as well.For example, five carriers of DL CC 1 1105, DL CC 2 1110, DL CC 3 1115,DL CC 4 1120, and DL CC 5 1125 are configured for an arbitrary UE 405.Assume that among the carriers, the DL CC 1 1105 and the DL CC 2 1110belong to a similar frequency band, and the other DL CCs belong toanother similar frequency band. An ENB 410 configures the DL CC 1 1105and the DL CC 2 1110 as one group, and configures the DL CC 3 1115, theDL CC 4 1120, and the DL CC 5 1125 as another group. While configuringthe carriers, the ENB 410 notifies the UE 405 of the group informationas well. For example, if the DL CC 1 1105 is an anchor carrier, the DLCC 1 1105 always maintains its activated state. Also, even the DL CC 21110 belonging to the same group as that of the DL CC 1 1105 alwaysmaintains its activated state. The UE 405 receives a DL assignment overthe activated carrier. If a carrier indicator 515 of the received DLassignment indicates a carrier belonging to a group having already beenactivated, for example, if the carrier indicator 515 indicates a carrier#1 1130 or a carrier #2 1135, the UE 405 receives a PDSCH from theindicated carrier. If the received carrier indicator 515 indicates acarrier belonging to a group having not been activated yet, for example,if the carrier indicator 515 indicates a carrier #5 1140, the UE 405activates all carriers belonging to the same group as that of theindicated carrier, i.e., the DL CC 3 1115, the DL CC 4 1120, and the DLCC 5 1125.

FIG. 12 illustrates an operation of a UE according to the thirdexemplary embodiment of the present invention.

Referring now to FIG. 12, in step 1205, a UE 405 recognizes a group ofconfigured carriers. For example, the UE 405 may receive a CA messageand recognize a group to which configured carriers belong, based on theinformation indicating to which group specific carriers included in thereceived CA message belong.

Upon receiving a DL assignment in step 1207, the UE 405 checks a carrierindicator in the DL assignment in step 1210. If all carriers in the samegroup as that of indicated carriers have already been activated, the UE405 proceeds to step 1215. On the other hand, if there is at least onedeactivated carrier among the carriers in the same group as that of theindicated carrier, the UE 405 proceeds to step 1220.

In step 1215, the UE 405 receives a PDSCH from the carrier indicated inthe DL assignment. On the other hand, in step 1220, in step 1220, the UE405 activates a carrier(s) having not been activated yet among thecarriers in the same group as that of the carrier indicated in the DLassignment. Thereafter, in step 1225, the UE 405 receives a PDSCH fromthe carrier indicated in the DL assignment. The carrier, from which thePDSCH is received, may be a carrier from which a predetermined specificcarrier or DL assignment is received, as in the first exemplaryembodiment.

Fourth Exemplary Embodiment

FIG. 13 illustrates an example of an operation according to a fourthexemplary embodiment of the present invention.

Referring now to FIG. 13, a carrier indicator 515 may be eitherconfigured or not configured for every individual UE. Hence, a method ofactivating carriers using a carrier indicator 515 cannot be used for aUE 405 for which the carrier indicator 515 is not configured. The fourthexemplary embodiment of the present invention provides a method oftemporarily activating all carriers for a specific period uponoccurrence of a specific event, instead of using the carrier indicator515, and then determining whether to activate the carriers depending onthe reception/non-reception of a DL assignment while in the temporarilyactivated state. The specific event may be, for example, an event inwhich a specific DL scheduling assignment is received from an anchorcarrier. For instance, a five carriers of a DL CC 1 1305, a DL CC 21310, a DL CC 3 1315, a DL CC 4 1320, and a DL CC 5 1325 are configuredfor an arbitrary UE. If the DL CC 1 1305 is an anchor carrier, thiscarrier always maintains its activated state. Upon receiving a DLassignment 1330 over the DL CC 1 1305 at an arbitrary time, a UE 405temporarily activates all of configured DL carriers. As to a temporaryactivation period, an ENB 410 determines the temporary activation periodand notifies it to the UE 405 through a call setup process. It isassumed in FIG. 13 that the temporary activation period is a period ofthree subframes. The UE 405 starts receiving PDCCHs of the temporarilyactivated DL carriers. Upon receiving a DL assignment 1335 over the DLCC 2 1310 at an arbitrary time that the temporarily activated state hasnot been ended, the UE 405 activates the DL CC 2 1310 and then maintainsthe activated state unless the ENB 410 explicitly instructsdeactivation, or unless another specific timer expires. Upon receiving aDL assignment 1340 over the DL CC 4 1320 at an arbitrary time when thetemporarily activated state has not been ended, the UE 405 activates theDL CC 4 1320. Upon expiry of the temporary activation period, the UE 405deactivates the remaining carriers, i.e., the DL CC 3 1315 and the DL CC5 1325, which have not been actually activated until the temporaryactivation period expires.

FIG. 14 illustrates an operation of a UE according to the fourthexemplary embodiment of the present invention.

Referring now to FIG. 14, in step 1405, a UE 405 receives a DLassignment over a specific carrier. The specific carrier, a carrieralways maintaining its activated state, may be an anchor carrier or aspecial carrier.

Upon receiving a DL assignment over an anchor carrier, which meansreception of a command to temporarily activate all carriers having notbeen activated yet, the UE 405 temporarily activates all carriers not inan activated state among the configured carriers in step 1410. Thetemporarily activation means maintaining an activated state for aspecific short period in order to receive a normal carrier activationcommand. The UE 405 may start a specific timer, for example, a temporaryactivation timer, and end the temporarily activated state if the timerexpires. In step 1415, the UE 405 checks if the temporarily activatedstate is ended. It may be considered that the temporarily activatedstate is ended if, for example, the temporary activation timer expires.If the temporarily activated state has not been ended, the UE 405proceeds to step 1420, and if the temporarily activated state has beenended, the UE 405 proceeds to step 1425.

In step 1420, the UE 405 checks whether a DL assignment for atemporarily activated carrier is received. Upon receiving a DLassignment for a temporarily activated carrier, which means reception ofa command to normally activate the DL assignment, the UE 405 proceeds tostep 1430. Upon failure to receive a DL assignment for the temporarilyactivated carrier, the UE 405 returns to step 1415 and checks whetherthe temporary activation is ended.

In step 1430, the UE 405 normally activates the DL carrier over which ithas received the DL assignment during the temporary activation. Normalactivation means maintaining an activated state for a comparatively longtime compared with the temporary activation. In the normal activation,the UE 405 may start a specific timer, for example, a normal activationtimer, and maintain the activated state until the timer expires, oruntil it explicitly receives a deactivation command from the ENB 410.

In step 1425, the UE 405 deactivates the carriers which are not normallyactivated, i.e., the carriers still being in the temporarily activatedstate, or the carriers over which the UE 405 has failed to receive a DLassignment while the temporary activation timer is in operation.

Fifth Exemplary Embodiment

An ENB 410 may transmit a DL assignment not for the purpose ofactivating other carriers, but for the purpose of transmitting data overa pertinent carrier. Even in this case, it is not preferable to activateother DL carriers. A fifth exemplary embodiment of the present inventionprovides a method of allowing a DL assignment to correspond to a carrieractivation command only when the DL assignment includes predeterminedspecific information, for example, size information of DL data, therebysolving the above-mentioned problems.

Activating a carrier for an arbitrary UE 405 corresponds to an increasein the amount of DL data to be transmitted to the UE 405. Therefore,other carriers may be defined to be activated only when the amount ofdata scheduled using a DL assignment is greater than or equal to aspecific reference value, or only when the amount of transmissionresources scheduled using a DL assignment is greater than or equal to aspecific reference value. To control the carrier activation moreprecisely, the amount of DL data scheduled using an arbitrary DL carrierand a combination of carriers indicated to be activated may be definedin advance. Table 1 below shows examples of the amount of DL datascheduled using an arbitrary DL carrier and the combination of carriersindicated to be activated.

TABLE 1 Amount of data scheduled using DL assignment (size of MAC PDU)Combination of activated carriers x₁ DL CC 2 x₂ DL CC 2, DL CC 3 x₃ DLCC 2, DL CC 3, DL CC 4 . . . . . . x_(n) ALL DL CCs

Also, the combination of activated carriers may be mapped to the numberof scheduled resource blocks instead of the amount of data. Table 2below shows examples of the number of scheduled resource blocks and thecombination of activated carriers.

TABLE 2 Amount of resources scheduled using DL Combination of assignment(number of resource blocks) activated carriers n₁ DL CC 2 n₂ DL CC 2, DLCC 3 n₃ DL CC 2, DL CC 3, DL CC 4 . . . . . . n_(n) ALL DL CCs

If priorities of configured carriers are set in advance, the combinationof activated carriers may be replaced with the number of carriers. Forexample, if priorities of configured carriers are set in order of DL CC2, DL CC 3, DL CC 4, and DL CC 5, then a relationship between the amountof scheduled resources and the number of carriers to be additionallyactivated may be set in advance as shown in Table 3 below. Also, arelationship between the amount of scheduled data and the number ofcarriers to be additionally activated may be set in advance as shown inTable 4 below.

TABLE 3 Amount of resources scheduled using DL assignment (number ofresource blocks) Number of activated carriers n₁ 1 n₂ 2 n₃ 3 n₄ 4

TABLE 4 Amount of data scheduled using DL assignment (size of MAC PDU)Number of activated carriers x₁ 1 x₂ 2 x₃ 3 x₄ 4

For example, upon receiving a DL assignment in which the number ofresource blocks is n2 (or the amount of scheduled data is x2), a UE 405additionally activates two carriers with higher priority among thecarriers having not been activated yet. If DL CC 1 and DL CC 2 havealready been activated, the UE 405 additionally activates DL CC 3 and DLCC 4 with higher priority among the carriers having not been activatedyet.

FIG. 15 illustrates an operation of a UE according to the fifthexemplary embodiment of the present invention.

Referring now to FIG. 15, in step 1505, a UE 405 receives activationcommand setting information from an ENB 410. The activation commandsetting information is information specifying relationships between theamount of data (or the amount of resources) scheduled using a DLassignment received from a specific DL carrier and the number of, orsets of, DL carriers to be activated. The activation command settinginformation may be defined to activate all DL carriers if, for example,the amount of data scheduled using a DL assignment is greater than orequal to X bits (or if the number of scheduled resource blocks isgreater than or equal to a threshold n). The activation command settinginformation may be defined to activate a specific DL carrier(s) if thespecific amount of data (or the specific number of resource blocks) isscheduled as shown in Tables 1, 2, 3, and 4. In this case, theactivation command setting information is a set of unit information, andthe unit information may be the amount of data (or the number resourceblocks) scheduled using a DL assignment and a set of carriers to beactivated, as defined in each row of

Tables 1 and 2, or may be the amount of data (or the number resourceblocks) scheduled using a DL assignment and the number of carriers to beadditionally activated, as defined in each row of Tables 3 and 4. If theamount of scheduled data or the number of resource blocks is mapped tothe number of carriers to be additionally activated as defined in Table3 or 4, an ENB 410 informs a UE 405 of priority of each individualcarrier using a control message.

Upon receiving a DL assignment from a specific carrier in step 1510, theUE 405 checks in step 1515 whether the DL assignment serves as a carrieractivation command as well. If the amount of data or the number ofresource blocks, scheduled by the received DL assignment, is equal tothe amount of data or the number of resource blocks, predetermined bythe activation command setting information, then the received DLassignment serves as a carrier activation command as well, and the UE405 proceeds to step 1520. In step 1520, the UE 405 determines a carrierto be activated, based on the activation command setting information.For example, if the activation command setting information is configuredto activate all DL carriers upon receiving a DL assignment of X bytes ormore, the UE 450 activates all DL carriers upon receiving a DLassignment that schedules data of X bytes or more. If the activationcommand setting information is configured as defined in Table 1, the UE405 activates a DL CC 2 upon receiving a DL assignment that schedulesX1-byte data. If the activation command setting information isconfigured as defined in Table 2, the UE 405 activates carrierscorresponding to a specific number of resource blocks upon receiving aDL assignment that schedules the specific number of resource blocks. Ifthe activation information is configured as defined in Table 3, uponreceiving a DL assignment scheduling specific data, the UE 405additionally activates carriers, the number of which corresponds to theamount of scheduled data, in order of high priority, among the carriersbeing not activated presently. If the activation information isconfigured as defined in Table 4, upon receiving a DL assignmentscheduling a specific number of resource blocks, the UE 405 additionallyactivates carriers, the number of which corresponds to the number ofscheduled resource blocks, in order of high priority, among the carriersbeing not activated presently.

In step 1525, the UE 405 receives a PDSCH according to the PDSCH-relatedinformation included in the DL assignment.

FIG. 16 illustrates a UE for the first to fifth exemplary embodiments ofthe present invention.

Referring now to FIG. 16, a UE includes a transceiver 1605, atransmission/reception and carrier activation (Tx/Rx & CA) controller1610, a Multiplexing/Demultiplexing (MUX/DEMUX) unit 1620, a controlmessage handler 1635, and various upper layer units 1625 and 1630.

The transceiver 1605 receives data and a specific control signal over aDL carrier, and transmits data and a specific control signal over a ULcarrier. When a plurality of carriers are aggregated, the transceiver1605 transmits/receives data and control signals over the plurality ofcarriers.

The transmission/reception and carrier activation controller 1610controls the transceiver 1605 to transmit UL data or receive DL dataaccording to the control signal, for example, the schedule commandprovided by the transceiver 1605. Upon receiving a DL assignment, thetransmission/reception and carrier activation controller 1610 determineswhether to activate carriers, depending on specific information in thereceived DL assignment. For example, in the first exemplary embodimentof the present invention, if a carrier indicator in the DL assignmentindicates a carrier having not been activated yet, thetransmission/reception and carrier activation controller 1610 controlsthe transceiver 1605 to activate the indicated carrier. In the secondexemplary embodiment of the present invention, if the DL assignment is acarrier activation command, the transmission/reception and carrieractivation controller 1610 activates carriers instructed to beactivated, by analyzing a bitmap. In the third exemplary embodiment ofthe present invention, the transmission/reception and carrier activationcontroller 1610 activates the carriers belonging to the same group asthat of the carrier indicated by the carrier indicator of the DLassignment. In the fourth exemplary embodiment of the present invention,upon receiving a DL assignment over a specific carrier, thetransmission/reception and carrier activation controller 1610temporarily activates the remaining carriers, and upon receiving a DLassignment for a specific carrier in the temporarily activated state,the transmission/reception and carrier activation controller 1610normally activates the specific carrier. In the fifth exemplaryembodiment of the present invention, the transmission/reception andcarrier activation controller 1610 receives a DL assignment over aspecific carrier, and activates specific carriers if the amount of datascheduled in the DL assignment is equal to a specific value (or fallswithin a specific range).

The MUX/DEMUX unit 1620 multiplexes the data generated in the upperlayer units 1625 and 1630 or the control message handler 1635, ordemultiplexes the data received from the transceiver 1605 and deliversthe demultiplexed data to the appropriate upper layer units 1625 and1630 or the control message handler 1635.

The control message handler 1635 handles a control message transmittedby the network and performs a required operation. The upper layer units1625 and 1630 may be constructed for associated services independently.The upper layer units 1625 and 1630 process the data generated in userservices such as a File Transfer Protocol (FTP) and a Voice overInternet Protocol (VoIP) and deliver the processed data to a MUX unit,or process the data transferred by a DEMUX unit and deliver theprocessed data to an upper-layer service application.

Sixth Exemplary Embodiment

Only some of a plurality of configured carriers may be in an activatedstate. That is, configured carriers operate in any one of an activatedstate and a deactivated state. In order to normally operate inconfigured carriers, a UE 405 periodically performs specific measurementon the configured carriers. The measurement means an action in which theUE 405 receives a signal from a target carrier instructed to be measuredand measures strength of the signal at intervals of a specific period.Given that one of the major reasons defining the deactivated state isthe minimization of power consumed in a deactivated carrier, performingmeasurement on activated carriers and deactivated carriers at the sameperiod may significantly reduce the effects by the deactivated state.

A sixth exemplary embodiment of the present invention provides a methodand apparatus of applying different measurement periods to activatedcarriers and deactivated carriers.

Prior to a description of the present exemplary embodiment, a process ofmeasuring a specific carrier by a UE 405 will be described. The purposeof the measurement is to detect wireless channel conditions of a servingcell or its neighbor cells and make appropriate decisions. That is, thepurpose is to make proper decisions for UE mobility support, etc., basedon the measurement results on a specific measurement target such as aserving cell and its neighbor cells. Given the inaccuracy of themeasurements implied in the UE 405, a measurement value filtered frominstantaneous measurement values for a specific period is used insteadof the instantaneous measurement values, for the decision making. Thefiltered measurement value is derived from the following Equation (1),and a UE calculates a filtered measurement result using the measurementresults obtained by performing measurements for a specific period calleda measurement period at a specific interval called a measurementinterval. The filtered measurement result value may be calculated byEquation (1) below.

filtered measurement result=α*‘measurement result for currentmeasurement period’+(1−α)*‘filtered measurement result for previousmeasurement period’  (1)

FIG. 17 illustrates an example of a measurement process according to anexemplary embodiment of the present invention.

Referring now to FIG. 17, for example, for an arbitrary N-th measurementperiod 1715, a UE 405 performs measurements 1705 a predetermined numberof times, and calculates a filtered measurement result using onerepresentative value, e.g., an average value, from the measurementresults at a time 1725. This process is repeated in every measurementperiod, for example, (N+1)th measurement period 1720 and time 1730.

As illustrated, the measurement interval and the measurement period areinformation for controlling how frequently the UE 405 performs themeasurement and how frequent the filtered measurement result is updated.

In the case of activated carriers, since DL/UL datatransmission/reception may likely occur frequently, additional powerconsumption is not significant despite frequent measurement. On theother hand, in the case of deactivated carriers, the frequentmeasurement may cause significant additional power consumption, becausethe measurement is a unique event. In the present exemplary embodimentinspired by the above and other problems, different measurement periodsand different measurement intervals are applied to the activatedcarriers and the deactivated carriers.

FIG. 18 illustrates an example of an operation according to the sixthexemplary embodiment of the present invention.

Referring now to FIG. 18, describing the present exemplary embodiment inmore detail, a measurement interval 1810 and a measurement period 1815,which were applied to a connected UE conventionally, are applied intactto an activated carrier. Conventionally, a connected UE adjusts ameasurement interval and a measurement period according to adiscontinuous reception (DRX) operation. So, there is no need toseparately signal the measurement interval and the measurement period.On the other hand, it is preferable for a measurement interval and ameasurement period of a deactivated carrier to be set as long values ifpossible, in order to minimize the power consumption of a UE, and themeasurement interval and the measurement period should be setindependently of the measurement interval and the measurement periodbeing used in the activated carrier. In the present exemplaryembodiment, a measurement interval 1820 and a measurement period 1825for a deactivated carrier are explicitly signaled using a controlmessage.

FIG. 19 illustrates an operation of a UE according to the sixthexemplary embodiment of the present invention.

Referring now to FIG. 19, in step 1905, a UE 405 configures a newcarrier using a carrier configuration message. The carrier configurationmessage includes a measurement interval and a measurement period aswell, which are to be applied to a deactivated carrier. The twoparameters may be signaled individually. Otherwise, only one parameteris signaled and the other parameter may be derived from the signaledparameter. For example, it is provided that a relationship between ameasurement period and a measurement interval, as defined in Equation(2) below, is always satisfied.

measurement period=5*measurement interval  (2)

Even though only one parameter is signaled, the other parameter can becalculated from the signaled value.

In step 1910, the UE 405 starts measurement on the configured arbitrarycarrier. In step 1915, the UE 405 checks if the carrier subjected tomeasurement is in an activated state or a deactivated state. In case ofthe activated state, the UE 405 determines a measurement interval and ameasurement period to be applied, taking a DRX situation of the carrierinto account, and performs measurement on the carrier in step 1920. Ifthe carrier is in the deactivated state, the UE 405 performs measurementby applying a measurement interval and a measurement period instructedto be applied to the deactivated state in step 1925. That is, the UE 405performs measurement on the carrier at every measurement interval,calculates a filtered measurement result using a representative value ofthe value measured at every measurement period, and makes decisions onmobility support or Channel Quality Indicator (CQI) of the UE 405 basedon the calculated filtered measurement result value.

Seventh Exemplary Embodiment

FIG. 20 illustrates a mismatch between aggregated DL carriers in frametiming according to an exemplary embodiment of the present invention.

Referring now to FIG. 20, CA is made between carriers transmitted fromthe same ENB. Since carriers transmitted from the same ENB have the sameframe timing, it is not necessary to separately acquire frame timings ofthe aggregated carriers. However, in a special case where a repeater isused, even the signals transmitted from the same ENB may not becoincident with each other in frame timing. For instance, in the casewhere an arbitrary UE 2005 receives a carrier with a frequency f1 from arepeater 2010 and a carrier with a frequency f2 from an ENB 2015, aframe timing of the carrier f1 may be different from a frame timing ofthe carrier f2. When aggregating such carriers having different frametimings, the UE 2005 should acquire synchronization for the carriers.Acquiring synchronization for carriers means a process of receiving aSynchronization Channel (SCH) from a certain cell having a certaincarrier and detecting a frame boundary of the cell through the cellsearch process described in 3GPP TS36.213. To receive a synchronizationchannel and detect a frame boundary, the UE 2005 should receive a signalof a pertinent carrier for a period of several to tens of milliseconds(msec). Hence, if the long measurement interval and measurement periodfor a deactivated carrier are applied, excessive time may be consumed inthe synchronization acquisition process.

A seventh exemplary embodiment of the present invention provides amethod, in which while transmitting a CA message to a UE, an ENB 2015indicates its execution/non-execution of a DL synchronization processfor an arbitrary carrier, and for a carrier instructed to perform the DLsynchronization process, a UE 2005 operates as if a conventionalconnected UE non-supporting a DRX operation performs a synchronizationprocess, instead of performing a synchronization process using themeasurement interval and the measurement period for a deactivatedcarrier, for an initial specific period even in a deactivated state.

FIG. 21 illustrates an example of an operation according to the seventhexemplary embodiment of the present invention.

Referring now to FIG. 21, in the seventh exemplary embodiment of thepresent invention, upon receiving a carrier configuration message,depending on whether a DL synchronization acquisition process isrequired for a newly configured carrier, a UE 2005 performs in step 2105measurement using a measurement interval and a measurement period setfor a deactivated state until the carrier is activated, if the DLsynchronization acquisition process is not required, and performs instep 2110 measurement using a measurement interval and a measurementperiod set for an activation state once the carrier is activated. If theDL synchronization acquisition process for the newly configured carrieris required, the UE 2005 performs in step 2115 measurement using theshortest measurement interval for the first x msec, or untilsynchronization for the carrier is acquired. Because a connected UEnon-supporting DRX performs measurement using the shortest measurementinterval, it may be expressed that if the DL synchronization acquisitionprocess for the newly configured carrier is required, the UE 2005operates in step 2115 as if it is a connected UE non-supporting DRX, forthe first x msec, or until synchronization for the carrier is acquired.Since then, the UE 2005 performs measurement using a measurementinterval and a measurement period, which are set for the deactivatedstate, or if it makes transition to the activated state, the UE 2005performs in step 2120 measurement using a measurement interval and ameasurement period, which are set for the activated state. Step 2110 maybe replaced with an operation of attempting synchronization acquisitionby continuously receiving a signal of a pertinent carrier for the firstx msec, or until acquisition for the carrier is acquired.

FIG. 22 illustrates the overall operation according to the seventhexemplary embodiment of the present invention.

Referring now to FIG. 22, upon determining to configure an arbitrarycarrier for a UE 2005, an ENB 2015 transmits a carrier configurationmessage to the UE 2005 in step 2215. The carrier configuration messageincludes information related to a carrier to be configured, and a DLsync group ID of the carrier. The information related to a carrier to beconfigured includes, as described above, a center frequency, BW, PCI,etc. Strictly speaking, because aggregating or configuration carriers isequivalent to aggregating or configuration specific cells of thecarriers, the terms carrier and carrier/cell are used in the meaning inthe seventh exemplary embodiment of the present invention. The ENB 2015may group carriers/cells sharing the same frame timing, and the DL syncgroup ID is information indicating a DL sync group to which an arbitraryDL carrier/cell belongs. If a DL carrier/cell is configured, whichbelongs to the same DL sync group as that of a carrier/cell whose DLsync has already been established, then the UE 2005, instead ofestablishing DL synchronization for the DL carrier/cell, determines thata frame timing of the newly configured DL carrier/cell has already beensynchronized and is equal to a frame timing of a DL carrier/cellbelonging to the same DL sync group. If a DL carrier/cell is configured,which belongs to a DL sync group whose synchronization has not beenestablished, the UE 2005 performs a DL synchronization process with thenewly configured DL carrier/cell.

In step 2220, the UE 2005 determines whether to perform a DLsynchronization process by checking a DL sync group ID of the newlyconfigured DL carrier/cell. If there is no carrier/cell belonging to theDL sync group to which the newly configured DL carrier/cell belongs,among the carriers/cells whose synchronization has already beenestablished and maintained, the UE 2005 performs a DL synchronizationprocess for the newly configured DL carrier/cell in step 2225. The DLsynchronization process is a process of detecting a frame timing byreceiving a synchronization channel of a newly configured carrier/cell,and in this process, the UE 2005 receives a signal by applying theshortest measurement interval to the newly configured carrier. Ifsynchronization for the carrier/cell has been established or a specifictime of x msec has elapsed, the UE 2005 stops applying the shortestmeasurement interval and performs measurement using a measurementinterval and a measurement period for a deactivated carrier. The reasonfor limiting an upper limit of a period to which the shortestmeasurement interval is applied, to x msec is to prevent the UE 2005from failing to acquire DL synchronization for a long time because ofthe poor channel condition of a DL carrier whose DL synchronizationshould be established. Upon establishing DL synchronization for apertinent carrier, or upon failure to establish DL synchronization for apertinent carrier for x msec, the UE 2005 transmits a message reportingthe success/failure of establishment of DL synchronization to the ENB2015 in step 2230. The ENB 2015 does not activate the DL carrier thathas failed in establishment of DL synchronization, until establishmentof DL synchronization is successful.

FIG. 23 illustrates an operation of a UE according to the seventhexemplary embodiment of the present invention.

Referring now to FIG. 23, in step 2305, a UE 2005 receives a carrierconfiguration message. The carrier configuration message includesinformation related to a DL carrier/cell instructed to be configured, anID of a DL sync group to which a DL carrier/cell belongs, timerinformation, etc.

In step 2310, the UE 2005 determines whether to perform DLsynchronization process by checking a DL sync group ID of the DLcarrier/cell to be newly configured. If there is a DL carrier/cellbelonging to the DL sync group to which the DL carrier/cell to be newlyconfigured belongs, among the DL carriers/cells whose DL synchronizationis being maintained, then the UE 2005 proceeds to step 2315. If there isno DL carrier/cell belonging to the DL sync group of the DL carrier/cellto be newly configured, among the DL carriers/cells whose DLsynchronization is being maintained, then the UE 2005 proceeds to step2325. In step 2315, the UE 2005 matches a frame timing of the newlyconfigured DL carrier/cell to a frame timing of a carrier/cell whosesynchronization is being maintained and which belongs to the same DLsync group. In step 2320, the UE 2005 performs measurement on thecarrier/cell using a measurement interval and a measurement period for adeactivated carrier until it receives an activation command for thecarrier/cell.

The UE starts a timer in step 2325, and performs a specific operation toestablish DL synchronization for the newly configured carrier/cell instep 2330. To be specific, the specific operation is an operation ofacquiring a frame timing by receiving a synchronization channel from anindicated cell with the newly configured carrier. In performing thisoperation, the UE 2005 considers that the carrier is an activatedcarrier with DRX being not set, in order to use the shortest measurementinterval in receiving a signal of the carrier/cell. If establishment ofDL synchronization is successful or the timer expires in step 2335, theUE 2005 proceeds to step 2340, and upon failure in establishment of DLsynchronization, the UE 2005 returns to step 2330 and continues toattempt the DL synchronization establishment. In step 2340, the UE 2005checks whether DL synchronization establishment is successful. Ifsuccessful, the UE 2005 reports the success in DL synchronizationestablishment in step 2345. In step 2350, the UE 2005 performsmeasurement on the carrier using a measurement interval and ameasurement period for a deactivated carrier until it receives anactivation command for the carrier. Upon failure in DL synchronizationestablishment, the UE 2005 reports the fail in DL synchronizationestablishment to the ENB 2015 in step 2355. In step 2360, the UE 2005attempts DL synchronization establishment at intervals of a measurementinterval for a deactivated carrier.

Eighth Exemplary Embodiment

If a measurement period and a measurement interval for a deactivatedcarrier are set longer than a measurement period and a measurementinterval for an activated carrier as in the sixth exemplary embodimentof the present invention, a filtered measurement result of a deactivatedcarrier may be updated more slowly than a filtered measurement result ofan activated carrier, causing problems especially when the deactivatedcarrier is a carrier having the best channel condition. For example, ifa deactivated carrier has the best channel condition and a filteredmeasurement result of a carrier having the best channel condition isused in making decision on mobility, even though a channel condition ofa carrier, which was deactivated despite its best channel condition,deteriorates abruptly later, the deteriorated channel condition may beslowly reflected in the filtered measurement result because of the longmeasurement interval and measurement period for a deactivated carrier.While the deteriorated channel condition is not reflected in thefiltered measurement result, a UE may misjudge a carrier having the bestchannel condition, thus making wrong decisions.

To address the above and other problems, an eighth exemplary embodimentof the present invention provides a method in which if a carrier havingthe best channel condition is in a deactivated state, a UE notifies itto an ENB.

FIG. 24 illustrates an operation of a UE according to the eighthexemplary embodiment of the present invention.

Referring now to FIG. 24, in step 2405, a deactivation condition of anarbitrary activated carrier is met for a UE 2005. For example, thedeactivation condition may represent a lapse of a predetermined timeafter the carrier is activated. The UE 2005 deactivates a carriermeeting the deactivation condition in step 2410, and checks in step 2415whether the deactivated carrier is a carrier having the best channelcondition among the configured carriers. A carrier having the bestchannel condition may mean that the carrier has the best filteredmeasurement result for its Reference Signal Received Power (RSRP). Ifthe carrier meeting the deactivation condition has the best channelcondition, the UE 2005 transmits a control message reporting thedeactivation of the best carrier to an ENB 2015 in step 2420, and thenends the process. The control message may include information such as aPCI of a carrier deactivated and having the best channel condition and afiltered measurement result for RSRP of the carrier. If the deactivatedcarrier is not a best carrier, the UE 2005 ends the process.

Another example of the eighth exemplary embodiment of the presentinvention provides a method in which if a deactivation condition for acarrier having the best channel condition is met, a UE reports it to anENB and maintains an activated state thereof.

FIG. 25 illustrates another operation of a UE according to the eighthexemplary embodiment of the present invention.

Referring now to FIG. 25, in step 2505, a deactivation condition of anarbitrary activated carrier is met for a UE 2005. For example, thedeactivation condition may represent a lapse of a predetermined timeafter the carrier is activated. The UE 2005 checks in step 2510 whetherthe carrier meeting the deactivation condition is a carrier having thebest channel condition, among the configured carriers. If a deactivationcondition of the carrier having the best channel condition is met, theUE 2005 transmits a control message reporting the met deactivationcondition of the best carrier to an ENB in step 2515. The controlmessage may include information such as a PCI of a carrier having thebest channel condition and meeting the deactivation condition. In step2515, the UE 2005 continues to perform measurement by applying ameasurement period and a measurement interval for an activated state tothe related cell while maintaining the activated state of the carrier.In step 2520, if the channel condition of the carrier becomes poorerthan channel conditions of other carriers, the UE 2005 deactivates thecarrier. If the carrier meeting the deactivation condition is not a bestcarrier in step 2510, the UE 2005 deactivates the carrier in step 2525.

FIG. 26 illustrates a UE for the sixth, seventh, and eighth exemplaryembodiments of the present invention.

Referring now to FIG. 26, a UE includes a transceiver 2605, ameasurement & DL sync controller 2610, a MUX/DEMUX unit 2620, a controlmessage handler 2635, and various upper layer units 2625 and 2630.

The transceiver 2605 receives data and a specific control signal over aDL carrier, and transmits data and a specific control signal over a ULcarrier. When a plurality of carriers are aggregated, the transceiver2605 transmits/receives data and control signals over the plurality ofcarriers.

The control message handler 2635 performs a required operation byanalyzing a control message received from an ENB. In the sixth exemplaryembodiment of the present invention, the control message handler 2635delivers information such as a DRX interval and a measurement intervaland a measurement period for a deactivated carrier, which are includedin the received control message, to the measurement & DL sync controller2610. In the seventh exemplary embodiment of the present invention, thecontrol message handler 2635 adds a DL sync group ID of a DL carrier tobe newly configured to the above information in the received controlmessage.

If needed, the control message handler 2635 generates a control messageand delivers it to a lower layer. In the eighth exemplary embodiment ofthe present invention, if the measurement & DL sync controller 2610notifies ‘the met deactivation condition of the best carrier’ or ‘thedeactivation of the best carrier’, the control message handler 2635generates a control message and reports it to an ENB 2015. In the eighthexemplary embodiment of the present invention, the control message maybe generated in a MAC layer. In this case, if the deactivation conditionof the best carrier is met or the best carrier is deactivated, themeasurement & DL sync controller 2610 reports it to the MUX/DEMUX unit2620, and the MUX/DEMUX unit 2620 generates a control message andreports it to the ENB 2015.

The measurement & DL sync controller 2610 instructs a receiver toperform measurement at a required time, and calculates and manages afiltered measurement result by collecting the measurement results. Inthe sixth exemplary embodiment of the present invention, the measurement& DL sync controller 2610 determines a time for measurement consideringthe activated/deactivated state of each carrier, and controls a receiverfor the related carrier to receive a signal at the pertinent time. Inthe seventh exemplary embodiment of the present invention, themeasurement & DL sync controller 2610 determines thenecessity/non-necessity of DL synchronization establishment of a newlyconfigured carrier, and in case of the necessity of DL synchronizationestablishment, the measurement & DL sync controller 2610 controls thereceiver to continuously receive a signal for the carrier. Uponestablishment of DL synchronization, the measurement & DL synccontroller 2610 controls the receiver to perform measurement usingappropriate measurement period and measurement interval. In the eighthexemplary embodiment of the present invention, if a carrier deactivatedor meeting a deactivation condition is the best carrier, the measurement& DL sync controller 2610 reports it to the control message handler 2635or the MUX/DEMUX unit 2620.

The MUX/DEMUX unit 2620 multiplexes the data generated in the upperlayer units 2625 and 2630 or the control message handler 2635, ordemultiplexes the data received from the transceiver 2605 and deliversthe demultiplexed data to the appropriate upper layer units 2625 and2630 or the control message handler 2635.

The upper layer units 2625 and 2630, which may be made for associatedservices individually, process the data generated in user services suchas FTP and VoIP, and deliver the processed data to a MUX unit, orprocess the data transferred by a DEMUX unit and deliver the processeddata to an upper-layer service application.

Ninth Exemplary Embodiment

FIG. 27 illustrates a process of scrambling and descrambling a DLtraffic channel according to an exemplary embodiment of the presentinvention.

In a CA system, a new type of carrier is defined, which is called anextension carrier in which there is no synchronization channel with aPDCCH. The extension carrier provides only a PDSCH, and a DL assignmentis provided over a DL PDCCH of another carrier. User data transmittedover the PDSCH is scrambled for a reduction in inter-cell interference.This process will be described in more detail with reference to FIG. 27.Referring now to FIG. 27, an ENB 2015 inputs a bit stream 2705 to betransmitted to a user, to a specific scrambling unit 2710, and thescrambling unit 2710 converts the bit stream 2705 into scrambled data2715 using specific parameters and a specific algorithm. If thescrambled data 2715 is transmitted to a UE 2005, the UE 2005 inputs thereceived data to a descrambling unit 2720. The descrambling unit 2720converts the descrambled data into its original bit stream 2725 usingspecific parameters and a specific algorithm. The parameters being inputin the scrambling and descrambling processes include RNTI, PCI, and Ns.The RNTI is an ID called a C-RNTI that the UE 2005 uses in a cell wherethe PDSCH is transmitted/received. The PCI is a PCI of the cell wherethe PDSCH is transmitted/received. Ns is slot numbers of a subframe overwhich the PDSCH is transmitted. One subframe includes two slots, oneradio frame includes twenty slots, and every slot is assigned a uniquenumber ranging between 0 and 19. Ns is the slot numbers of the subframe.

It is natural that the above three parameters are required totransmit/receive a PDSCH over an extension carrier. In the extensioncarrier, since there is no synchronization channel, the slot numbers Nsdo not exist as well. For descrambling, a method of defining a PCI and aC-RNTI for an extension carrier and signaling them to a UE 2005 may beused, but this may cause an increase in PCI/C-RNTI management cost andsignaling overhead. In scrambling/descrambling a PDSCHtransmitted/received over an extension carrier, the present exemplaryembodiment uses the C-RNTI, PCI, and Ns of the cell in which a DLassignment is transmitted/received, instead of the PDSCH, therebysolving the above problems.

In summary, in the ninth exemplary embodiment of the present invention,for scrambling/descrambling of a PDSCH transmitted/received over anextension carrier, a UE ID (C-RNTI) used in the cell from which a DLassignment is received, a PCI of the cell from which a DL assignment isreceived, and slot numbers Ns of the subframe over which a DL assignmentis received.

FIG. 28 illustrates an operation of an ENB according to the ninthexemplary embodiment of the present invention.

Referring now to FIG. 28, in step 2805, an ENB 2015 determines totransmit a PDSCH to an arbitrary UE 2005 over an extension carrier. TheENB 2015 determines a carrier/cell, through a PDCCH of which it willtransmit a DL assignment for PDSCH scheduling of an extension carrier,in step 2810, and scrambles the PDSCH using parameters to be applied forscrambling of the PDSCH in step 2815. The parameters include a UE IDused in the cell in which a DL assignment is to be transmitted, a PCI ofthe cell in which a DL assignment is to be transmitted, and slot numbersNs of a subframe over which a DL assignment is to be transmitted. Instep 2820, the ENB 2015 transmits a PDSCH over an extension carrier in asubframe whose transmission was scheduled in step 2185, and transmits aDL assignment over the carrier/cell determined in step 2810.

FIG. 29 illustrates an operation of a UE according to the ninthexemplary embodiment of the present invention.

Referring now to FIG. 29, in step 2905, a UE 2005 receives a DLassignment. In step 2910, the UE 2005 checks if the received DLassignment is a DL assignment for scheduling a PDSCH of an extensioncarrier. For example, if a carrier indicator in the received DLassignment indicates a carrier ID of an extension carrier, the DLassignment is a DL assignment for scheduling a PDSCH of an extensioncarrier.

If the received DL assignment is a DL assignment for scheduling a PDSCHof an extension carrier, the UE 2005 proceeds to step 2915, and if thereceived DL assignment is not a DL assignment for scheduling a PDSCH ofan extension carrier, the UE 2005 proceeds to step 2920.

In step 2915, the UE 2005 descrambles a received PDSCH using a UE IDused in the cell from which the PDSCH is received, a PCI of the cellfrom which the PDSCH is received, and slot numbers Ns of a subframe overwhich the PDSCH is received.

In step 2920, the UE 2005 descrambles a received PDSCH using a UE IDused in the cell from which a DL assignment is received, a PCI of thecell from which a DL assignment is received, and slot numbers Ns of asubframe over which a DL assignment is received. The UE ID used in thecell from which a DL assignment is received may be a C-RNTI used formasking of a DL assignment.

FIG. 30 illustrates an ENB for the ninth exemplary embodiment of thepresent invention.

Referring now to FIG. 30, an ENB includes a divider 3005, an extensioncarrier transmitter 3010, a plurality of ordinary carrier transmitters3015 and 3020, a scrambling parameter controller 3025, and a scheduler3030.

The scheduler 3030 makes decisions on scheduling taking into account theamount of DL traffic, the channel condition of a UE, etc. That is, thescheduler 3030 determines the time at which it will transmit data, theUE to which it will transmit data, the carrier through which it willtransmit data, and the amount of data it will transmit. Upon determiningto transmit DL data to an arbitrary UE, the scheduler 3030 determinesthrough which carrier it will transmit the data. Upon determining totransmit the data through an extension carrier, the scheduler 3030determines a carrier through which it will transmit a DL assignment. Bynotifying the decisions to the divider 3005 and an upper layer (notshown in the drawing), the scheduler 3030 controls the upper layer togenerate data in an indicated size and deliver it to the divider 3005.The divider 3005 delivers the data provided from the upper layer to anappropriate transmitter under control of the scheduler 3030. Thescheduler 3030 notifies the scheduling-related decisions to thescrambling parameter controller 3025, and if the DL data is transmittedthrough an ordinary carrier, the scrambling parameter controller 3025delivers PCI, C-RNTI, and Ns for the cell in which a PDSCH istransmitted, to a transmitter for the carrier. The transmitter scramblesdata using the parameters, and transmits the scrambled data in thecarrier through a specific procedure. If the DL data is transmittedthrough an extension carrier, the scrambling parameter controller 3025delivers PCI, C-RNTI, and Ns for the cell in which a DL assignment istransmitted, to a transmitter for the carrier. The transmitter performsan operation of scrambling data using the parameters.

FIG. 31 illustrates a UE for the ninth exemplary embodiment of thepresent invention.

Referring now to FIG. 31, a UE includes a transceiver 3105, a controller3110, a MUX/DEMUX unit 3120, a control message handler 3135, and variousupper layer units 3125 and 3130.

The transceiver 3105 receives data and a specific control signal over aDL carrier, and transmits data and a specific control signal over a ULcarrier. If a plurality of carriers are aggregated, the transceiver 3105transmits/receives data and control signals over the plurality ofcarriers.

The control message handler 3135 analyzes a control message receivedfrom an ENB 2015, and performs a necessary operation. Upon receiving aspecific control message, the control message handler 3135 checks UE IDsto be used in an ordinary carrier for individual carriers independently,and delivers them to the controller 3110.

The controller 3110 receives a DL assignment, determines from whichcarrier it should receive a PDSCH, and controls the transceiver 3105 toreceive the PDSCH from the determined carrier. If the carrier from whicha PDSCH is to be received is an extension carrier, the controller 3110controls the transceiver 3105 to descramble the PDSCH using C-RNTI, PCI,and Ns for the cell from which a DL assignment is received. If thecarrier from which a PDSCH is to be received is not an extensioncarrier, the controller 3110 controls the transceiver 3105 to descramblethe PDSCH using C-RNTI, PCI, and Ns for the cell from which the PDSCH isreceived.

The MUX/DEMUX unit 3120 multiplexes the data generated in the upperlayer units 3125 and 3130 or the control message handler 3135, ordemultiplexes the data received from the transceiver 3105 and deliversthe demultiplexed data to the appropriate upper layer units 3125 and3130 or the control message handler 3135.

The upper layer units 3125 and 3130, which may be made for associatedservices individually, process the data generated in user services suchas FTP and VoIP, and deliver the processed data to a MUX unit, orprocess the data transferred by a DEMUX unit and deliver the processeddata to an upper-layer service application.

Tenth Exemplary Embodiment

A tenth exemplary embodiment of the present invention provides a methodand apparatus for deactivating an activated carrier.

An ENB aggregates a plurality of carriers for a UE in case of anincrease in traffic for an arbitrary UE, and deactivates the aggregatedcarriers in case of a decrease in traffic, thereby minimizing powerconsumption by the UE. The carrier deactivation may be indicated using adeactivation signal. However, if a UE fails to receive the deactivationsignal, the carrier to be deactivated may remain in the activated state,causing unnecessary power consumption. To solve these problems, thetenth exemplary embodiment of the present invention provides a method inwhich by introducing a deactivation timer, a UE deactivates a DL carrierby itself if a specific condition is met. If there is no datatransmission/reception in an activated carrier for a predetermined time,a UE deactivates the carrier by itself To this end, the UE starts adeactivation timer if a DL carrier is activated, and restarts the timerupon receiving data from the DL carrier. If the timer expires, i.e., ifDL data has not been received from the DL carrier for a specific period,the UE deactivates the DL carrier by itself Since not only DL data butalso DL HARQ feedback are transmitted/received over a DL carrier, ifthere is a possibility that DL HARQ feedback will be received eventhough DL data is not received for a considerable period, the DL carriershould maintain its activated state. In the present invention, a UErestarts the deactivation timer every time it receives DL HARQ feedback,thereby preventing possible deactivation of a DL carrier expected toreceive DL feedback. This situation in which DL feedback is continuouslyreceived may correspond to, for example, an case in whichsemi-persistent transmission resources are activated in a UL carrierassociated with the DL carrier. In this case, in the UL carrierassociated with the DL carrier, UL transmission is periodicallyperformed, and a UE periodically receives DL HARQ feedback from the DLcarrier.

FIG. 32 illustrates an example of an operation of deactivating activatedcarriers according to the tenth exemplary embodiment of the presentinvention.

Referring now to FIG. 32, if a DL CC 1 3205, a DL CC 2 3210, a UL CC 13215, and a UL CC 2 3220 are aggregated for an arbitrary UE, the DL CC1and the UL CC1 are associated with each other, and the DL CC 2 and ULCC2 are associated with each other. If the DL CC 2 is activated at anarbitrary time 3225, a UE starts a deactivation timer for the carrier attime 3230. The timer is restarted every time data is received from thecarrier, for example, time 3235, or every time DL HARQ feedback isreceived, for example, times 3240 and 3245. The DL HARQ feedback istransmitted/received when UL transmission has occurred in a UL carrierassociated with the DL carrier, and the UL transmission may be, forexample, UL transmission over semi-persistent transmission resources.

At an arbitrary time, if DL data or DL HARQ feedback is no longerreceived from the DL carrier until the deactivation timer expires attime 3250, the UE deactivates the DL carrier.

FIG. 33 illustrates an operation of a UE according to the tenthexemplary embodiment of the present invention.

Referring now to FIG. 33, a UE activates an arbitrary DL carrier in step3305, and starts a deactivation timer for the DL carrier in step 3310.After starting the deactivation timer, the UE checks in step 3315whether the deactivation timer has expired, in every subframe. The UEproceeds to step 3325 if the deactivation timer has not expired, and tostep 3320 if the deactivation timer has expired. In step 3320, the UEdeactivates the DL carrier whose deactivation timer has expired, andthen ends the process.

In step 3325, the UE checks if DL data has been received from the DLcarrier in a pertinent subframe. The DL data's having been received maycorrespond to, for example, having received a PDSCH over the DL carrier.The DL data's having been received may correspond to having received aDL assignment indicating new DL data transmission over the DL carrier,or a DL assignment indicating DL data retransmission over the DLcarrier. The UE proceeds to step 3335 if data has been received in step3325, and to step 3330 if data has not been received. In step 3330, theUE checks if an HARQ feedback has been received from the DL carrier inthe pertinent subframe. The UE proceeds to step 3335 upon receiving anHARQ feedback. If neither the HARQ feedback nor the DL data have beenreceived in the subframe in step 3330, the UE returns to step 3315 andrepeats the same check process in the next subframe. In step 3335, theUE restarts the deactivation timer. In other words, the UE initializesand restarts the timer. For example, if the timer has already run xmsec, the UE sets a value of the timer to its initial value and restartsthe timer. Thereafter, the UE proceeds to step 3315 and repeats the samecheck process in the next subframe.

FIG. 34 illustrates another operation of a UE according to the tenthexemplary embodiment of the present invention.

With reference to FIG. 34, a description will be made of a method forminimizing the number of deactivation timers running at the same time,by stopping a deactivation timer for the DL carrier where a DL HARQfeedback is provided for a UL carrier, to which semi-persistenttransmission resources are allocated.

If semi-persistent transmission resources are allocated from anarbitrary UL carrier in step 3405, a UE proceeds to step 3410. Thesemi-persistent transmission resources' being activated (or allocated)means that semi-persistent transmission resources have been allocated toa UE over a DL PDCCH. The UE transmits UL data with the allocatedsemi-persistent transmission resources at a predetermined period.Semi-persistent transmission resources being allocated may be referredto as semi-persistent transmission resources' being activated.

In step 3410, the UE stops a deactivation timer for the DL carrier fromwhich an HARQ feedback will be received for the UL data to betransmitted through the semi-persistent transmission resources, and theninitializes a value of the timer. In other words, for the DL carrier,the UE is adapted not to perform its own deactivation caused byexpiration of the deactivation timer. The DL carrier from which an HARQfeedback will be received for the UL data transmitted oversemi-persistent transmission resources, may be determined in severaldifferent methods. For example, a DL carrier which is associated, interms of scheduling, with the UL carrier to which semi-persistenttransmission resources are to be allocated, may provide an HARQfeedback. A UL grant for an arbitrary UL carrier may be set to beprovided only through a specific DL carrier, and in this case, it isexpressed that the DL carrier is associated with the UL carrier in termsof scheduling. A UL carrier to which semi-persistent transmissionresources are allocated, and a DL carrier to provide an HARQ feedbackfor the UL carrier may be preset in a call setup process. Also, it maybe provided that an HARQ feedback for semi-persistent transmissionresources may be transmitted over a DL carrier through whichsemi-persistent transmission resource allocation messages are exchanged.

Thereafter, the UE waits until the UL semi-persistent transmissionresources are released. For reference, semi-persistent transmissionresources being released may be referred to as semi-persistenttransmission resources being deactivated. If the UL semi-persistenttransmission resources are released in step 3415, the UE starts in step3420 the deactivation timer which was stopped in step 3410, i.e., thedeactivation timer for the DL carrier that provided the HARQ feedbackfor the released semi-persistent transmission resources. In other words,the UE resumes the operation of deactivating a related DL carrier byitself upon expiration of the deactivation timer.

Eleventh Exemplary Embodiment

FIG. 35 illustrates an example of Radio Frequency (RF) reconfigurationaccording to an exemplary embodiment of the present invention.

Depending on the performance of a UE, RF should be reconfigured (orreadjusted) occasionally when DL CC is activated or deactivated. Forexample, if a UE has only one RF and aggregates carriers only in thesame frequency band, the UE may have to adjust (or configure) a centerfrequency of the RF according to the activation/deactivation ofcarriers. Referring now to FIG. 35, for example, if only a DL CC 1 3505is in an activated state, the center frequency of the RF is matched to acenter frequency 3515 of the DL CC1, whereas if only a DL CC 2 3510 isin an activated state, the center frequency of the RF is matched to acenter frequency 3520 of the DL CC2. If both the DL CC1 and the DL CC2are activated, the center frequency of the RF is matched to the center3525 between the DL CC1 and the DL CC2. The operation of adjusting acenter frequency of RF is needless when the UE has separate RFs for DLCCs individually. However, since a low-priced UE may have only one RF,it may require the above process of adjusting a center frequency of RFevery time DL CC is activated or deactivated. For reconfiguration (orreadjustment) of an RF center frequency, about hundreds of microsecondsare required generally. Because data transmission/reception isimpossible when a UE is reconfiguring an RF center frequency, data lossmay occur if the UE undergoes scheduling while reconfiguring the RFcenter frequency.

The present exemplary embodiment provides a method and apparatus inwhich if an event occurs in which an RF center frequency should bechanged, a UE reconfigures the RF center frequency in a subframe agreedupon in advance with an ENB, thereby preventing a data loss.

FIG. 36 illustrates an example of an operation of reconfiguring RFaccording to the eleventh exemplary embodiment of the present invention.

Referring now to FIG. 36, in step 3615, while reporting its ownperformance to an ENB 3610 in an initial call setup process or a processof transitioning to an RRC connected state, a UE 3605 notifies anindicator indicating the necessity/non-necessity of RF reconfiguration,as well. If the UE 3605 has a CA capability, and should reconfigure RFwhen activating or deactivating a carrier due to the limit of RF, the UE3605 sets the indicator as ‘Yes’ and reports it to the ENB 3610.

Thereafter, the ENB 3610 configures a plurality of carriers for the UE3605 through a normal control procedure with the UE 3605. In step 3620,the ENB 3610 transmits control information commanding the UE 3605 toactivate a carrier at the time it determines to be needed. The carrieractivation command may be control information of a MAC layer. Thecarrier activation command may undergo HARQ retransmission because it istransmitted in a common MAC PDU. Upon successfully receiving the carrieractivation command, the UE 3605 determines a subframe where RFreconfiguration is possible after a lapse of a predetermined periodsince the subframe where the command is received. For convenience ofdescription, the period for which a UE is allowed to perform RFreconfiguration is called an RF reconfiguration window. In step 3625,the UE 3605 performs RF reconfiguration in a first subframe, where theongoing data transmission/reception is affected despite execution of theRF reconfiguration, among the subframes in an RF reconfiguration window.A subframe where the ongoing data transmission/reception is affecteddespite execution of RF reconfiguration may include, for example, otherDL subframes except for a ‘subframe where an HARQ ACK/NACK is to bereceived’, a ‘subframe where semi-persistent transmission resources areallocated’, and a ‘subframe where an adaptive retransmission command foruncompleted UL transmission may be received’. That is, upon receiving aDL carrier activation command, a UE performs RF reconfiguration in afirst subframe other than (i) a subframe where an HARQ ACK/NACK is to bereceived, (ii) a subframe where semi-persistent transmission resourcesare allocated, and (iii) a subframe where an adaptive retransmissioncommand for uncompleted UL transmission may be received, among thesubframes in an RF reconfiguration window or until another specificperiod elapses since a lapse of a specific period from the time thecommand was received. If such DL subframes do not exist in the RFreconfiguration window, the UE 3605 performs RF reconfiguration in thefirst subframe in the RF reconfiguration window.

In step 3630, in the other subframes except for the subframe where RFreconfiguration is performed, the ENB 3610 may allocate a DL assignmentor transmit DL data to the UE 3605. In other words, even in the RFreconfiguration window, data transmission/reception is possible in theother subframes except for the subframe where the RF reconfiguration isperformed.

FIG. 37 illustrates an example of an RF reconfiguration window accordingto an exemplary embodiment of the present invention.

An RF reconfiguration window will be described in more detail withreference to FIG. 37.

If a MAC PDU with a carrier activation command is received in an N-thsubframe 3705, decoding of the MAC PDU is generally completed in an(N+1)th subframe 3710 and a command included in the MAC PDU is analyzed.According to the HARQ procedure of the LTE system, an HARQ feedback forthe MAC PDU is transmitted in an (N+4)th UL subframe 3715. If the MACPDU was successfully decoded, the feedback is an HARQ ACK, and becauseof a time difference between a DL subframe and a UL subframe, an ENBdetects in an (N+5)th subframe 3720 the fact that the HARQ ACK wasreceived, i.e., the fact that the DL carrier activation command wasnormally transmitted. Because the fact that a carrier activation signaltransmitted in an N-th subframe was normally handled is detected by anENB in an (N+5)th subframe, the ENB may perform a necessary operationfrom the next subframe, i.e., an (N+6)th subframe 3725. For thesereasons, it is preferable for an RF reconfiguration window to start witha subframe after a lapse of five subframes from the subframe where thecarrier activation command was received. As to a size (or a length) ofthe RF reconfiguration window, two to three subframes may be goodenough.

In exemplary embodiments of the present invention, it is assumed that astart point and a size of the RF reconfiguration window are set for eachUE individually by an ENB. However, fixed values may be used as thestart point and the size of the RF reconfiguration window. For example,if a carrier activation command is received in an Nth subframe, an RFreconfiguration window may be set as (N+6)˜(N+8). A size of the windowmay be unlimited.

FIG. 38 illustrates an operation of a UE according to the eleventhexemplary embodiment of the present invention.

Referring now to FIG. 38, in step 3805, a UE detects the necessity of RFreconfiguration by analyzing a control message for activating a DLcarrier. In step 3810, the UE determines a subframe where a MAC PDU withthe control message was received. For example, upon detecting the factin an (N+1)th subframe that an arbitrary MAC PDU includes a controlmessage indicating DL carrier activation, the UE determines the lastsubframe where the MAC PDU was received. Once received, the MAC PDU isdecoded after undergoing HARQ soft combining. In addition, a CRCoperation is performed thereon to check the success/fail in reception,and in case of CRC OK, the UE demultiplexes the MAC PDU by analyzing asubheader of the MAC PDU. Whether a carrier activation message isincluded in an arbitrary MAC PDU may be determined in the demultiplexingprocess. While a time required until a UE performs a demultiplexingprocess for a MAC PDU after completing the MAC PDU reception may varydepending on the implemented performance of the UE, it is general thatthe required time is much shorter than 1 msec. Therefore, step 3810 maybe implemented with a specific offset for implementation of the UE. Ifthe fact that carrier activation information is stored in a MAC PDU wasdetected by a UE in, for example, an X-th subframe, the UE may determinethat the MAC PDU was received in a (X−m)th subframe, where ‘m’ is aparameter dependent on UE implementation.

In step 3815, the UE waits until S subframes elapse since the subframewhere the MAC PDU was received, i.e., since the Nth subframe in theexample of FIG. 37. For example, the UE waits for the time at which anRF reconfiguration window starts. The parameter S indicating a startpoint of the RF reconfiguration window may be set for each UEindividually, or may be defined as a predetermined specific value.

In step 3820, the UE determines a certain subframe in the RFreconfiguration window, in which it will perform RF reconfiguration. Asize L of the RF reconfiguration window may be set for each UEindividually, or may be defined as a predetermined specific value. Instep 3825, the UE may perform RF reconfiguration in a first DL subframethat meets, for example, the following Condition 1 and falls within theRF reconfiguration window.

-   -   Condition 1: The subframe is not a subframe in which HARQ        ACK/NACK reception is not scheduled and an adaptive        retransmission command for uncompleted UL HARQ retransmission        may be received, and is a subframe in which no semi-persistent        transmission resources are configured.

For the UL data transmitted in an xth subframe, an HARQ ACK/NACK isreceived in an (x+4)th DL subframe. Therefore, if UL data transmissionwas performed between the time four subframes before a start of the RFreconfiguration window, and the subframe at which the RF reconfigurationwindow starts, then HARQ ACK/NACK reception for the UL data transmissionfalls within the RF reconfiguration window. The UE excludes the subframewhere an HARQ ACK/NACK is to be received, from the subframes where RFreconfiguration is to be performed.

When a UL grant is received in a yth subframe, a UL grant indicatingadaptive retransmission may be received in (y+8), (y+16), . . . ,(y+max_retrans*8)th subframes. The UE excludes the subframe where the ULgrant indicating adaptive retransmission may be received, from thesubframes where RF reconfiguration is to be performed.

Semi-persistent transmission resources may be allocated in order toefficiently use a service in which data having a specific size isgenerated periodically, such as VoIP. The semi-persistent transmissionresources are transmission resources which are automatically allocatedin a specific subframe which comes at a specific period, and may bereferred to as a configured DL assignment. Since DL data is transmittedin a DL subframe where a configured DL assignment is configured, if RFreconfiguration is performed in this DL subframe, a data loss may occur.So, the UE excludes the DL subframe where a DL assignment is configured,from the subframes where RF reconfiguration is to be performed.

If there is no subframe meeting Condition 1 among the subframes in theRF reconfiguration window, the UE selects the first subframe in the RFreconfiguration window as a subframe where RF reconfiguration is to beperformed. If a size of the window is infinity, the UE waits foroccurrence of a subframe meeting the above condition, and performs RFreconfiguration in the subframe meeting the above condition.

In step 3825, the UE reconfigures RF in the selected subframe.

If a UE should measure a frequency other than the current frequency, ora Radio Access Technology (RAT) other than the current RAT, an ENB mayallocate a measurement gap to the UE. The measurement gap is set tooccur once every 40 or 80 msec, and a length thereof is 6 msec. For aperiod of the measurement gap, the UE measures another frequency oranother RAT, and stops DL data reception and UL data transmission. Ifthe measurement gap exists at the time close to the time where a carrieractivation command is received, it is preferable to reconfigure RF inthe measurement-gap period.

FIG. 39 illustrates another operation of a UE according to the eleventhexemplary embodiment of the present invention.

An operation of performing RF reconfiguration preferentially in ameasurement-gap period will be described with reference to FIG. 39.

Referring now to FIG. 39, in step 3905, a UE detects the necessity of RFreconfiguration by analyzing a control message for activating a DLcarrier. Thereafter, in step 3910, the UE checks a subframe in which aMAC PDU with the control message is received.

In step 3915, the UE determines whether it can perform RFreconfiguration using a Measurement Gap (MG). For example, if thefollowing Condition 2 is met, the UE determines that it can perform RFreconfiguration using a measurement gap.

-   -   Condition 2: A measurement gap is set to occur in a specific        period, and the specific period includes a period including        subframes in which an RF reconfiguration window is ended in the        subframe where a UE recognizes the necessity of RF        reconfiguration.

In other words, upon recognizing the necessity of RF reconfiguration byreceiving a carrier activation message, the UE determines whether ameasurement gap will occur between the pertinent subframe and a subframewhere the RF reconfiguration window is ended. If it is determined thatthe measurement gap will occur, the UE proceeds to step 3920,determining that the check result in step 3910 is ‘True’. Otherwise, theUE proceeds to step 3925. In step 3920, the UE reconfigures RF in one ofthe subframes belonging to the measurement gap.

On the other hand, operations in step 3925 and its succeeding steps arethe same as those of the UE operation illustrated in FIG. 38, so adetailed description thereof is omitted. Steps 3925, 3930 and 3935 areequal to steps 3815, 3820 and 3825, respectively.

In the UE operations illustrated in FIGS. 38 and 39, a time of 1 msec orless is assumed to be consumed for RF reconfiguration. While thisassumption is valid in most cases, a reconfiguration delay longer thanthis may occur depending on UEs. In this case, the UE notifies an ENB ofthe RF reconfiguration delay in advance in a UE performance reportmessage (see step 3615 in FIG. 36), and performs RF reconfiguration inspecific consecutive subframes beginning from the subframe meetingCondition 1 or 2. If the time consumed for RF reconfiguration rangesfrom (y−1) msec to y msec, the UE selects y subframes beginning from thesubframe meeting Condition 1 in step 3820 or 3930, instead of selectingone subframe. If there are no subframes meeting Condition 1, the UEselects y subframes beginning from the first subframe in the RFreconfiguration window. The other operations are equal to those in thecase where the RF reconfiguration delay is 1 msec or less, so adescription thereof is omitted.

FIG. 40 illustrates an operation of an ENB according to the eleventhexemplary embodiment of the present invention.

Referring now to FIG. 40, upon determining to activate a carrier, an ENBtransmits a carrier activation command to a UE in step 4005. Aftertransmitting a MAC PDU with the carrier activation command storedtherein to the UE, upon receiving an HARQ ACK for the MAC PDU in step4010, the ENB determines in step 4015 a subframe where the UE willreconfigure RF for the carrier activation. The ENB determines asubframe(s) meeting Condition 1 in the RF reconfiguration window, as anRF reconfiguration subframe. Also, the ENB determines, as an RFreconfiguration subframe, a subframe(s) that meets Condition 2 andexists between the last subframe where the MAC PDU was transmitted andthe subframe where the RF reconfiguration window is ended. In step 4020,the ENB determines not to schedule the UE in the RF reconfigurationsubframe.

While the tenth and eleventh exemplary embodiments of the presentinvention have been described in connection with the case where carriersare activated, these two exemplary embodiments may also be applied tomany other cases where RF reconfiguration is needed, for example, thecase where carriers are deactivated. In particular, given that RFreconfiguration for carrier activation should be performed as rapidly aspossible but RF reconfiguration for carrier deactivation may put up withsome delays, during carrier activation, an ENB may allow a UE toreconfigure RF in a predetermined subframe, for example, in a subframe aspecific interval after the time the MAC PDU indicating carrieractivation was received (i.e., the window is not used), and duringcarrier deactivation, the ENB may allow the UE to reconfigure RF in afirst subframe meeting Condition 1 or 2 beginning from a subframe aspecific interval after the time the MAC PDU indicating carrierdeactivation was received (i.e., an window with an infinite size isused).

FIG. 41 illustrates a UE operation of selecting a subframe in which RFis to be reconfigured during carrier activation and deactivationaccording to an exemplary embodiment of the present invention.

Referring now to FIG. 41, in step 4105, a UE recognizes the necessity ofRF reconfiguration by analyzing a control message for activating a DLcarrier. Thereafter, in step 4110, the UE determines a subframe where aMAC PDU with the control message was received. Step 4110 is the same asstep 3810, so a detailed description thereof is omitted. In step 4115,the UE determines whether the control message indicates activation ordeactivation of an arbitrary carrier. Since the control message containsbitmap information indicating states of carriers configured for a UE,one control message may activate or deactivate a plurality of carriers.If the control message indicates activation of an arbitrary carrier, theUE proceeds to step 4120, and if the control message indicatesdeactivation of an arbitrary carrier, the UE proceeds to step 4125. Ifthe control message indicates both activation and deactivation, forexample, if the control message indicates activation for a carrier 1,and deactivation for a carrier 2, the UE proceeds to step 4120.

In step 4120, the UE reconfigures RF after waiting for a specific numberS of subframes beginning from the subframe where the MAC PDU with thecontrol message indicating the activation of a carrier was received. Theparameter S may be set for each UE individually, or may be defined as apredetermined specific value.

In step 4125, the UE reconfigures RF in a subframe meeting a specificcondition, after waiting for a specific number S of subframes beginningfrom the subframe where the MAC PDU with the control message indicatingthe deactivation of a carrier was received. The specific condition is tominimize the impact on the ongoing operation, and for example, it ispossible to define a first subframe meeting Condition 1 as the subframemeeting a specific condition. Also, if measurement gaps are set,subframes belonging to the nearest measurement gap may be the subframesmeeting a specific condition.

FIG. 42 illustrates a UE according to the eleventh exemplary embodimentof the present invention.

Referring now to FIG. 42, the UE includes a transceiver 4205, atransmission/reception and RF reconfiguration (Tx/Rx & RFReconfiguration) controller 4210, a MUX/DEMUX unit 4220, a controlmessage handler 4235, and various upper layer units 4225 and 4230.

The transceiver 4205 receives data and a specific control signal over aDL carrier, and transmits data and a specific control signal over a ULcarrier. When a plurality of carriers are aggregated, the transceiver4205 transmits/receives data and control signals over the plurality ofcarriers. The transceiver 4205 includes various units including an RFunit.

The transmission/reception and RF reconfiguration controller 4210controls the transceiver 4205 to transmit UL data and receive DL dataaccording to a control signal, for example, a scheduling command,provided by the transceiver 4205. Upon receiving a carrier activationcommand from the MUX/DEMUX unit 4220, the transmission/reception and RFreconfiguration controller 4210 determines a subframe where it willreconfigure RF, and controls the transceiver 4205 to reconfigure RF inthe determined subframe.

The MUX/DEMUX unit 4220 multiplexes the data generated in the upperlayer units 4225 and 4230 or the control message handler 4235, ordemultiplexes the data received from the transceiver 4205 and deliversthe demultiplexed data to the appropriate upper layer units 4225 and4230 or the control message handler 4235.

The control message handler 4235 handles a control message transmittedby the network and performs a required operation. The upper layer units4225 and 4230, which may be constructed for associated servicesindependently, process the data generated in user services such as a FTPand a VoIP and deliver the processed data to a MUX unit, or process thedata transferred by a DEMUX unit and deliver the processed data to anupper-layer service application.

FIG. 43 illustrates an ENB according to the eleventh exemplaryembodiment of the present invention.

Referring now to FIG. 43, an ENB includes a transceiver 4305, acontroller 4310, a MUX/DEMUX unit 4320, a control message handler 4335,various upper layer units 4325 and 4330, and a scheduler 4340.

The transceiver 4305 receives data and a specific control signal over aUL carrier, and transmits data and a specific control signal over a DLcarrier. When a plurality of carriers are aggregated, the transceiver4305 transmits/receives data and control signals over the plurality ofcarriers.

The MUX/DEMUX unit 4320 multiplexes the data generated in the upperlayer units 4325 and 4330 or the control message handler 4335, ordemultiplexes the data received from the transceiver 4305, and deliversthe multiplexed/demultiplexed data to the appropriate upper layer units4325 and 4330 or the control message handler 4335. The MUX/DEMUX unit4320 also multiplexes the control message, for example, a carrieractivation message, transferred by the controller 4310, and transmitsthe multiplexed message to a UE. The control message handler 4335generates a specific control message and delivers the generated messageto the MUX/DEMUX unit 4320, or handles a control message provided by theMUX/DEMUX unit 4320. The upper layer units 4325 and 4330, which may beconstructed for associated UEs or services independently, process thedata generated in user services such as a FTP and a VoIP and deliver theprocessed data to a MUX unit, or process the data transferred by a DEMUXunit and deliver the processed data to an upper-layer serviceapplication.

Upon receiving an HARQ ACK for a carrier activation message, thecontroller 4310 determines a subframe where RF reconfiguration is to beperformed, and delivers information on the subframe to the scheduler4340.

The scheduler 4340 performs a scheduling operation so as not to schedulethe UE in the RF reconfiguration subframe.

As is apparent from the foregoing description, the present exemplaryembodiments can ensure rapid carrier activation, and minimize theinefficiency caused by transmitting a carrier activation command with aDL assignment.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

1.-19. (canceled)
 20. A method for measuring a carrier by a UserEquipment (UE) in a mobile communication system supporting carrieraggregation, the method comprising: receiving a parameter formeasurement of a carrier in a deactivated state, from an Evolved Node B(ENB); in performing measurement on a carrier in an activated state,determining a measurement interval and a measurement period taking aDiscontinuous Reception (DRX) operation into account and measuring thecarrier at the determined measurement interval for the determinedmeasurement period; and in performing measurement on the carrier in thedeactivated state, determining a measurement interval and a measurementperiod using a parameter related to at least one of a measurementinterval and a measurement period indicated by the ENB, and measuringthe carrier at the determined measurement interval for the determinedmeasurement period.
 21. The method of claim 20, wherein the determiningof the measurement interval and the measurement period for thedeactivated carrier comprises determining a remaining parameteraccording to a predetermined rule if the ENB indicates one of parametersrelated to the measurement interval and the measurement period.
 22. AUser Equipment (UE) in a mobile communication system supporting carrieraggregation, the UE comprising: a receiver for receiving a parameter formeasurement of a carrier in a deactivated state, from an Evolved Node B(ENB); and a controller for, in performing measurement on a carrier inan activated state, determining a measurement interval and a measurementperiod taking a Discontinuous Reception (DRX) operation into account andmeasuring the carrier at the determined measurement interval for thedetermined measurement period; and in performing measurement on thecarrier in the deactivated state, determining a measurement interval anda measurement period using a parameter related to at least one of ameasurement interval and a measurement period indicated by the ENB, andmeasuring the carrier at the determined measurement interval for thedetermined measurement period.
 23. The UE of claim 22, wherein in thedetermining of the measurement interval and the measurement period forthe deactivated carrier, the controller determines a remaining parameteraccording to a predetermined rule if the ENB indicates one of parametersrelated to the measurement interval and the measurement period.
 24. Amethod for activating a carrier by a User Equipment (UE) in a mobilecommunication system supporting carrier aggregation, the methodcomprising: receiving a carrier activation command from an Evolved NodeB (ENB); determining a time at which an operation required for carrieractivation is to be performed; and performing the operation required forcarrier activation at the determined time.
 25. The method of claim 24,further comprising: receiving a carrier deactivation command from theENB; determining a time at which an operation required for carrierdeactivation is to be performed; and performing the operation requiredfor carrier deactivation at the determined time.
 26. The method of claim25, wherein each of the operation required for carrier activation andthe operation required for carrier deactivation is a Radio Frequency(RF) reconfiguration operation.
 27. The method of claim 24, wherein thetime at which the operation required for carrier activation is to beperformed is a subframe that is separated by a predetermined period froma subframe where the carrier activation command was received.
 28. Themethod of claim 25, wherein the time at which the operation required forcarrier deactivation is to be performed is one of a plurality ofsubframes which are separated by a predetermined period from a subframewhere the carrier deactivation command was received.
 29. A UserEquipment (UE) in a mobile communication system supporting carrieraggregation, the UE comprising: a receiver for receiving a carrieractivation command from an Evolved Node B (ENB); a controller fordetermining a time at which an operation required for carrier activationis to be performed, and performing the operation required for carrieractivation at the determined time.
 30. The UE of claim 29, wherein ifthe receiver receives a carrier deactivation command from the ENB, thecontroller determines a time at which an operation required for carrierdeactivation is to be performed, and performs the operation required forcarrier deactivation at the determined time.
 31. The UE of claim 30,wherein each of the operation required for carrier activation and theoperation required for carrier deactivation is a Radio Frequency (RF)reconfiguration operation.
 32. The UE of claim 29, wherein the time atwhich the operation required for carrier activation is to be performedis a subframe that is separated by a predetermined period from asubframe where the carrier activation command was received.
 33. The UEof claim 30, wherein the time at which the operation required forcarrier deactivation is to be performed is one of a plurality ofsubframes which are separated by a predetermined period from a subframewhere the carrier deactivation command was received.